1. Technical Field
The present invention relates to a process for efficiently producing an aminoalkylsulfonic acid in an industrial scale, and a method of salt exchange for an aminoalkylsulfonate salt.
2. Prior Art
Aminoalkylsulfonic acids are useful compounds as intermediate raw materials such as skin cleansing agents consisting of soap and shampoo, surfactants and pH buffers, and drug raw materials.
Further, since aminoalkylsulfonic acids are amphoteric compounds having a strongly acidic functional group together with an amine group, it is expected that a fatty acid soap having different properties can be prepared by neutralizing a fatty acid with taurine or N-methyltaurine, which are a type of said compound, together with a strong alkali such as sodium hydroxide, to form a counterion bond between a carboxyl group of the fatty acid and an amine group of the amphoteric compound.
As a method for producing aminoalkylsulfonic acids, the following methods are known; for example, (1) a method for reacting ethyleneimine, sulfurous acid gas and water [see, e.g. JP-B-40-23007 (p. 1), JP-B-47-16807 (p. 1), etc.], (2) a method for heating N-methylaminoethane sulfate salt at 120–210° C. [see, e.g. JP-B-46-2087 (p. 1)], (3) a method for oxidation of 2,2-disubstituted thiazolidine with hydrogen peroxide, followed by hydrolysis [see, e.g. JP-A-57-26654 (p. 1–2)], (4) a method for reacting 2-aminoethanol sulfate ester with sodium sulfite [see, e.g. Journal of the Chemical Society, p. 4 (1943)], (5) a method for reacting a hydrogen halide salt of 2-halogenoethylamine with a sulfite salt [see, e.g. Journal of the American Chemical Society, Vol. 58, p. 191 (1936)], (6) a method for reacting a sulfite salt in an aqueous solution heated at temperature not lower than 50° C. with a halogenated alkylamine [see, e.g. WO 84/00958 (p. 5 and 20), JP-A-60-23360 (p. 1 and 3), JP-A-4-149168 (p. 1–3), etc.].
However, these methods have the following problems. Namely, the method (1) has problems such as difficult to control of reaction temperature due to generation of an extremely exothermic reaction; low yield due to side reactions such as polymerization of ethyleneimine; and difficult to handle to ethyleneimine and sulfurous acid gas as starting materials in an industrial scale due to toxicities. The method (2) has a problem of difficult to handle production in an industrial scale due to a reaction at high temperature. The method (3) has problems such as use of hydrogen peroxide which is difficult-to-handle in view of safety; and complicated operations requiring recovery and reuse of ketone type as by-products. The method (4) has problems such as heating for long period due to extremely slow reaction of sulfate esters with sodium sulfite, thereby resulting in low yield due to production of ethanolamine as a by-product by hydrolysis of sulfate esters during the reaction; difficult to separate and recovery monoethanolamine as a by-product. Further, the method (5) and (6) have a problem of difficult to separate and recovery sulfite salts required to be used in excess amount.
Furthermore, the following methods are known as methods for producing an aminoalkylsulfonic acid from an aminoalkylsulfate salt: for example, (I) a method for reacting ammonium aminoethanesulfonate with hydrogen chloride, followed by extracting resulting aminoethanesulfonic acid with 95% ethanol and cooling the ethanol aqueous solution to precipitate an objective compound [see, e.g. Industrial and Engineering Chemistry, Vol. 39, P. 906 (1947)]; and (II) a method for reacting an aqueous solution of sodium aminoethanesulfonate with a mineral acid such as sulfuric acid and hydrogen chloride, followed by concentrating the resulting aqueous solution of aminoethanesulfonic acid to crystallize a part of sodium chloride as impurities at high temperature not lower than 80° C., and dilute the mother liquid with water and cooling to obtain an objective compound as crystal [see, e.g. DE 1122540 (p. 3–4 and 13), JP-A-6-345717 (p. 2–4) etc.].
However, the method (I) has problems such as an undesirable industrial process due to a large amount of ethanol to be used for extraction; repeated operations of the extraction to obtain high purity product; complicated treatment to be required for separating ammonium hydrochloride as impurities which is contained in almost the same amount to an objective compound; and undesirable disposal of the impurity in view of environmental conservation. In addition, the method (II) has problems such as complicated operations to be required for difficult to separate inorganic substances such as sodium chloride as impurities and a water-soluble aminoalkylsulfonic acid in an aqueous solution; and repeated operations to be required for recovery of filtrate and crystallization because an object compound can be crystallized only partly by this method.
Under such circumstances, development of a method for efficiently producing a high purity aminoalkylsulfonic acid in an industrial scale is required.